Electric circuit breaker with toggle positioning means



Nov. 3, 1964 K. w. KLEIN ETAL ELECTRIC CIRCUIT BREAKER WITH TOGGLE POSITIONING MEANS 2 Sheets-Sheet 1 Filed July 25, 1962 F/GJ.

INVENTORS KE/TH W. KLEIN, DAV/0 B. POWELL,

ATTORNEY.

Nov. 3, 1964 K. w. KLEIN ETAL 3,155,803

ELECTRIC CIRCUIT BREAKER WITH TQGGLE POSITIONING MEANS Filed July 25, 1962 2 Sheets-Sheet 2 INVENTORS. KE/ TH W KLE/N, DAV/0 B. POWELL,

ATTORNEY. v

United States Patent poration of New York Filed July 25, 1962, Ser. No. 212,432 4 Claims. (Cl. 200-153) Our invention relates to electric circuit breakers, and more particularly to electric circuit breakers of the type having a movable contact arm and operating mechanism for moving said contact arm between open and closed circuit positions including a releasable cradle member and a pair of toggle links interconnecting the cradle member and the movable contact arm.

In such circuit breaker mechanisms, release of the releasable member takes place upon the occurrence of certain abnormal current conditions, permitting the toggle links to collapse, and the movable contact arm to move to open-circuit position.

When such automatic opening is caused by short-circuit conditions, such as 10,000 amperes, the movable contact arm moves to open position with such force that it sometimes rebounds toward closed circuit position, prolonging the arcing process if the arc has not been extinguished, or permitting the arc to re-strike if it has been extinguished.

The operating spring which, for example, in the oil" position strongly resists such rebound action, is relaxed when the parts move to the tripped position, because of the release of the releasable member. Accordingly, it ordinarily does not act to prevent such rebound.

It is an object of the invention to provide an electric circuit breaker of the type described including means for inhibiting the tendency of the movable contact arms to rebound toward closed position following an automatic opening operation.

It is another object of the invention to provide an electric circuit breaker of the type described including means for initiating a rapid collapse of the toggle linkage, whereby to accelerate the contact opening action upon automatic operation.

It is another object of the invention to provide an electric circuit breaker of the type described which is extremely compact, and yet capable of producing high contact pressure and wide contact separation in the opencircuit condition.

In accordance with the invention in one form, an electric circuit breaker is provided including a pivotally supported contact arm and a releasable cradle member, releasably held by current responsive means. A pair of toggle links is provided interconnecting the pivotally supported contact arm and the releasable cradle member. Manually operable handle means is also provided, interconnected by a tension spring to the knee of the toggle linkage, whereby reciprocal movement of the operating handle causes alternate straightening and collapsing action of the toggle linkage and corresponding opening and closing movement of the movable contact arm. The operating mechanism furthermore includes a relatively stationary stop member and projections on the upper toggle links engageable with the stop member to accelerate and to accentuate the collapsing act-ion of the toggle linkage, and also to inhibit the rebounding action of the movable contact arms toward closed position following automatic opening operation.

The invention will be more fully understood from the following detailed description, and its scope will be pointed out in the appended claims.

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In the drawings,

FIGURE 1 is a top plan view of an electric circuit breaker incorporating the present invention, a portion of the insulating casing thereof being broken away;

FIGURE 2 is a combination side elevation view and sectional view of the circuit breaker of FIGURE 1, the sectional portion of the view being taken substantially on the line 22 of FIGURE 1;

FIGURE 3 is a side elevation view of the operating mechanism of the circuit breaker of FIGURES 1 and 2, the parts being shown in the automatically opened or tripped position;

FIGURE 4 is a view similar to FIGURE 3, the parts being shown in the manual 0 position;

FIGURE 5 is a fragmentary view on enlarged scale of a portion of the operating mechanism of the circuit breaker of FIGURE 1, and

FIGURE 6 is a fragmentary side elevation view of a portion of the operating mechanism, the parts being shown in the automatically tnipped position similar to FIG- URE 3.

Referring to the drawings, the invention is shown as incorporated in an electric circuit breaker including an insulating casing comprising a base it} and a cover 11. Three line terminals 12 are supported on the insulating base it} at one end thereof, and three load terminals 13 are supported on the opposite end of the insulating base, substantially in alignment with the corresponding line terminals. Operation of the circuit breaker is adapted to control electrical continuity between the corresponding line and load terminals 12, 13, the portion of the circuit breaker between each corresponding pair of line and load terminals being known as a pole. Accordingly, the circuit breaker as shown in FIGURE 1 is a three-pole circuit breaker. It will be understood, however that the present invention is equally applicable to circuit breakers having a number of poles other than three, such for instance as one and two-pole circuit breakers.

Each of the line terminals 12 is connected to and supported by a conductive insert 14 carried by the base it The terminal 12 is connected to the insert 1e and also to a terminal strap 15 by means of a screw 16. The terminal strap 15 extends inwardly within the circuit breaker proper and carries a relatively stationary contact 17 on the inner end thereof. A relatively movable contact 18 is also provided, carried by a movable contact support member 19, which in turn is pivotally supported by the pivot pin 2%} on a movable contact arm 21. The contact arm 21 is pivotally supported in the insulating casing by suitable pivotal supports, not shown, and is connected by a contact cross-arm 22 to corresponding contact arms of the other two poles of the circuit breaker. A compression spring 21A is provided between the contact carrying member 19 and the contact arm 21, for the purpose of providing contact pressure in the on position.

Referring to FIGURE 2, the current-path through the central pole of the circuit breaker is shown. The movable contact support member 18 is connected by a flexible connector 24 to an intermediate conductor 25, which is connected by means of screw 26 to a line terminal member 2'7 of a current responsive assembly or trip unit 2.3. The terminm member 27 passes through the trip unit 28, energizing its current-responsive means, not shown, and having a projecting portion 29 serving as a load terminal. The load terminal 29 serves to support the load terminal members 13 which are connected thereto by being bolted to a conductive insert 36 by means of a screw 31.

The movable contact arm 21 is adapted to be operated between open and closed circuit positions by means of an operating mechanism comprising a pair of side frames or plates 32, only one shown, see FIGURE 2. The side plates 32 serve to support the operating mechanism parts, including a releasable latched member or cradle 33 pivotally supported on the side frames 32 by a pivot pin 34. The cradle member 33 is biased in a clockwise direction as shown, by means to be described, and includes a latch portion 35 which is rcleasably held by a cooperating latch member 36. The latch member 36 is adapted to be moved to release the cradle 33 upon the occurrence of predetermined current conditions through any one of the pole portions of the circuit breaker.

A toggle linkage assembly is also provided interconnecting the cradle member 33 and the contact arm 21 comprising a pair of upper toggle links 37 pivotally connected to the cradle 33 by a pivot pin 38, and a pair of lower toggle links 39 pivotally connected at one end to the contact arm 21 by the pivot pin 29. The toggle links 37 and 39 are interconnected by a knee pivot pin 46-. For strengthening purposes, the upper toggle links 37 are interconnected by a bracing pin 37B, and the cradle member 33 is provided with an arcuately shaped aperture 33C, providing clearance for the pin 373.

The toggle links 37 and 39 are adapted to be operated between collapsed and straightened conditions, to move the contact arm 21 between open and closed circuit positions with respect to the stationary contact 17, by means of a manually operable handle member 42. The handle member 42 is carried by the handle support member 43. The handle support member 43 is generally U-shaped, see FIGURE 5, and is pivotally supported upon pivot pins 44 carried by the side frames 32. The handle support member 43 is connected by means of a pair of tension type springs 45, to the knee pin 4% of the toggle linkage.

Oscillating movement of the handle 42 between on and off positions as indicated in FIGURE 2, carries the upper end of the tension springs 45 across the line of centers of the knee pin and the pivot pin 38, thereby moving the toggle linkage between corresponding straightened and collapsed conditions.

For the purpose of limiting movement of the knee of the toggle linkage, beyond the straightened position to the right as viewed in FIGURE 2, the knee pin 40 is provided with an enlarged-diameter central portion 40A. The portion 40A lies in the central plane of the mechanism, i.e., in the same plane as the releasable member 33. When the toggle is moved to straightened condition, the portion 40A strikes an edge portion 33A (see FIG- URE 4) of the cradle 33, closely adjacent the pivot pin 34.

Contact Acceleration and Rebound Prevention In accordance with the invention, the upper toggle links 37 are each provided with an extension or enlarged portion 37A, and a stop pin 50 is provided, carried by the frame side plates 32.

It will be observed by reference to FIGURE 2, that when the parts are in the manual on position, the cradle member 33 being in latched position, the projections 37A are close to or in contact with the pin 50.

On the occurrence of predetermined current conditions through any of the poles of the circuit breaker, the latch member 36 is moved by the trip unit 28, thereby releasing the latch portion 35 of the cradle member 33.

The action of the tension springs on the knee pin 4-0 is such as exert, through the upper toggle links 37, a force on the cradle member 33, tending to rotate it in clockwise direction. Substantially at the beginning of this movement following release of the cradle 33, the portions 37A of the upper toggle links 37 engage the pin 59. As the cradle member 33 continues to rotate in clockwise direction, the interaction of the pin and the portions 37A of the upper toggle links 37 forces the toggle linkage 37-39 to collapse by movement of the knee pin 40 to the left as viewed. This accelerates the opening movement of the movable contact arm 21 and its associated contact carrying member 1) and contact 18.

As the tripping operation continues, the knee pin 40 is cammcd to the left by the action of the pin 50 on the extension 37A, while the pivot pin 38 is moved to the right by the rotataing action of the cradle member 33. The net effect of this is to cause the pin 38 to cross the line of action of the springs 45 so that when the cradle 33 moves to the fully tripped position, as shown in FIG- URE 3, the action of the springs 45 on the upper toggle links 37 is such as to tend to rotate them in a clockwise, i.e., collapsing, direction, rather than a counterclockwise, i.e., straightening, direction. The action of the tension springs 45 in the tripped position, is therefore such as to tend to move the toggle linkage 37-39, in a further collapsed direction. This is true, regardless of whether the handle 42 is manually held in the on position, or not. See FIGURE 6.

In accordance with the invention, the interengagement of the pin 50 and the extensions 37A of the upper toggle links 37 serves as a substantial deterrent to any tendency of the movable contact arms 21 to rebound back toward closed position following tripping movement as previously described. This aspect of the invention may be best understood by reference to FIGURE 6. In this figure, the parts are shown in the position which they occupy following an automatic opening operation. It will be observed that the pin 50 serves as a stop to limit movement of the contact arms 21 in opening direction.

Since the springs 45 provide a relatively high force, such for example as approximately pounds in the fully extended position, the contact arms 21 are moved to automatically tripped condition at an extremely high rate of speed. Upon striking the stop pin 59, there is a tendency of the contact arms 21 to rebound toward closed circuit position. If such rebound movement should occur, even to the extent of permitting partial movement of the movable contact toward closed position, it would create the danger of a restrike of the arc, with serious adverse effects.

In FIGURE 6, the force tending to cause rebound or reclosing movement of the contact arm 21 is indicated by the arrow F. It will be observed that movement of the contact arm 21 toward closed position has the effect of tending to rotate the upper toggle links 37 counterclockwise about their pivotal connection 38 with the cradle member 33.

It will be observed further, that if it were not for the extensions 37A of the upper toggle links 37, this movement would be permitted without movement of the cradle member 33, and therefore, the pivot point 40 could move along a path as designated by the letter A in FIGURE 6. The path A, which is concentric about the pin 38, extends substantially at right angles to the direction of elongation of the springs 45. Such motion, therefore, could occur, without substantial elongation of springs 45, and therefore without substantial resistance by these springs.

Because of the inter-action of the extension 37A with the pin 50, however, it is not possible for the contact arm 21 to move toward reclosed position without moving the cradle member 33 counterclockwise about its pivot 34. Such reclosing movement, according to the present invention, tends to cause the pivot 40 to move along a path generally as indicated at B in FIGURE 6, more nearly concentric about the pivot pin 34 of the cradle 33.

It will be observed that movement of the pivot pin 40 along the path B is not possible without causing substantial elongation of the tension springs 45. A very sub stantial opposing force, therefore, is brought into effect, opposing movement of the contact arm toward reclosed position. In an actual assembly, for instance, it has been found that the ratio of the force opposing movement of the contact arm 21 toward reclosed position in the case where extensions 37A and pin 50 are provided, as compared to a construction in which these are omitted, is in the order of 5 to 1.

The pin 50 also serves the further function of providing a stop for the cradle 33 in its rotation in a clockwise direction when tripping occurs. Referring to FIGURE 4,

the portion 333 of the cradle 33 engages the pin 50, limiting clockwise rotation of the cradle 33.

While the invention has been shown in only one particular embodiment, it will be readily apparent that many modifications thereof may be made. It is therefore intended, by the appended claims, to cover all such modifications as fall within the true spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric circuit breaker comprising:

(a) an insulating casing,

(b) at least one stationary contact mounted in said insulating casing,

(c) an elongated movable contact arm pivotally supported in said insulating casing and carrying a movable contact member movable by said contact arm into and out of engagement with said stationary contact,

(d) operating means in said casing for operating said contact arm between open and closed circuit positions comprising a mechanism frame fixedly mounted in said casing and a releasable cradle member pivotally mounted on said frame,

(0) a pair of toggle links interconnecting said cradle member and said movable contact arm, said toggle links comprising a pair of upper toggle links and a pair of lower toggle links interconnected by a knee pin,

(f) a manually operable handle member supported in said casing,

(g) a tension spring interconnecting said handle member and said knee pin of said toggle linkage,

(h) reciprocal movement of said handle member causing collapsing and straightening movement of said toggle linkage,

(i) said upper toggle links having a portion engaging said frame and restraining said toggle links in a partially collapsed condition following release of said releasable cradle member.

2. An electric circuit breaker comprising:

(a) an insulating casing,

(b) at least one stationary contact mounted in said insulating casing,

(c) at least one movable contact mounted in said insulating casing,

(d) an elongated contact arm pivotally mounted in said insulating casing and carrying said movable contact,

(e) means for operating said contact arm between open and closed circuit positions comprising a releasable cradle member pivotally supported in said insulating casing,

(7) said operating means also comprising an interconnected toggle link assembly comprising a pair of upper toggle links connected at one end to said cradle member and a pair of lower toggle links at one end to said contact arm and a knee pin interconnecting said upper and lower pairs of toggle links,

(g) a manually operable handle member pivotally supported in said insulating casing,

(h) a tension spring interconnecting said handle member and said knee pin of said toggle links, I

(i) reciprocal movement of said handle member causing collapsing and straightening movement of said toggle linkage and moving said contact arm between open and closed circuit positions respectively,

(j) a stationary stop member fixedly supported in said insulating casing adjacent said pivotal support of said releasable cradle member.

(k) said pair of upper toggle links including a portion engaging said stop member upon release of said releasable member and forcing said toggle linkage to assume a relatively collapsed position following release of said releasable member.

3. An electric circuit breaker as set forth in claim 2 wherein said toggle linkage is biased by said tension spring in collapsing direction in the at rest condition following release of said releasable cradle member,

(a) said upper toggle links including a portion disposed closely adjacent said stop member in said at rest position, whereby rebound movement of said movable contact arm toward said closed position causes said upper toggle links to engage said stop member and to resist said rebound movement of said contact arm.

4. An electric circuit breaker as set forth in claim 2 References Cited in the file of this patent UNITED STATES PATENTS Rowe et a1. May 26, 1953 Walker et a1. June 21, 1960 

1. AN ELECTRIC CIRCUIT BREAKER COMPRISING: (A) AN INSULATING CASING, (B) AT LEAST ONE STATIONARY CONTACT MOUNTED IN SAID INSULATING CASING, (C) AN ELONGATED MOVABLE CONTACT ARM PIVOTALLY SUPPORTED IN SAID INSULATING CASING AND CARRYING A MOVABLE CONTACT MEMBER MOVABLE BY SAID CONTACT ARM INTO AND OUT OF ENGAGEMENT WITH SAID STATIONARY CONTACT, (D) OPERATING MEANS IN SAID CASING FOR OPERATING SAID CONTACT ARM BETWEEN OPEN AND CLOSED CIRCUIT POSITIONS COMPRISING A MECHANISM FRAME FIXEDLY MOUNTED IN SAID CASING AND A RELEASABLE CRADLE MEMBER PIVOTALLY MOUNTED ON SAID FRAME, (E) A PAIR OF TOGGLE LINKS INTERCONNECTING SAID CRADLE MEMBER AND SAID MOVABLE CONTACT ARM, SAID TOGGLE LINKS COMPRISING A PAIR OF UPPER TOGGLE LINKS AND A PAIR OF LOWER TOGGLE LINKS INTERCONNECTED BY A KNEE PIN, (F) A MANUALLY OPERABLE HANDLE MEMBER SUPPORTED IN SAID CASING, (G) A TENSION SPRING INTERCONNECTING SAID HANDLE MEMBER AND SAID KNEE PIN OF SAID TOGGLE LINKAGE, (H) RECIPROCAL MOVEMENT OF SAID HANDLE MEMBER CAUSING COLLAPSING AND STRAIGHTENING MOVEMENT OF SAID TOGGLE LINKAGE, (I) SAID UPPER TOGGLE LINKS HAVING A PORTION ENGAGING SAID FRAME AND RESTRAINING SAID TOGGLE LINKS IN A PARTIALLY COLLAPSED CONDITION FOLLOWING RELEASE OF SAID RELEASABLE CRADLE MEMBER. 